You've heard of bomb sniffing dogs. But what about bomb sniffing plants?

Plants can't actually "sniff" of course. But scientists have genetically engineered plants that turn white when they sense tiny amounts of TNT in the air.

Turning White...

It makes sense that plants would work as threat detectors. Because they can't run and hide, over millions of years many plants have evolved ways of detecting threats and protecting themselves. For example, some plants release toxins when they're threatened by a hungry insect looking for a meal.

Scientists working with tobacco plants and a plant called arabidopsis used DNA to reprogram the plants' protein signaling process. When the engineered plants detect TNT, the hijacked process makes chlorophyll drain from the leaves, leaving them a ghostly white.

Still An Experiment

Bomb detecting plants aren't quite ready to make their debut in airport security zones. At the moment, the experimental plants take hours to "de green" in the presence of explosives. But scientists are working on plants that would take only minutes to change colors.

Scientists say that they should be able to turn the trick in any kind of plant. And they should be able to engineer plants to detect just about anything--such as radon or other potentially harmful gasses in homes.

Read More:

• Bomb-sniffing plants to the rescue (MSNBC)